From U.S. Pat. No. 8,245,971 B2, a control surface in which the external and internal sides are each embodied with one reinforcing structure has become known. The reinforcements are integrated into the surfaces of the control surface. The control surface is formed by an external plate and an internal plate which are prefabricated, for example, by RTM (Resin Transfer Molding). In this prior art, long stretched-out profiles of the external and/or internal plate which extend at the external and/or internal plate essentially at right angles with respect to each other are provided as reinforcements.
The known design, however, is directed to the introduction of uniformly distributed loads which are essentially diverted linearly at the edges of the component. However, the known design is not very well suited for diverting non-uniformly distributed loads with a weight-optimized design. Therefore, the known design is disadvantageous in that the arrangement of the reinforcements is not optimally adapted to non-uniform loads in aviation. It in particular turned out to be disadvantageous that the load introduction through the mounting of the control surface at the airplane's wing is not sufficiently provided for. Moreover, a comparatively high number of reinforcements is required which increase fabrication efforts and weight in a disadvantageous manner.
AT 409 482 B discloses a spoiler which comprises fittings with two bearings and a joint. Moreover, reinforcing structures radially emerging from the joint are provided. The spoiler may be manufactured by resin transfer molding in one operation with the fittings as composite fiber part. However, this spoiler has a comparatively high weight.
In U.S. 6,270,039 B1, fittings for connecting a control surface to the wing of an airplane are described.
US 2009072090 A1 and US 2013/011605 A1 show control surfaces with different reinforcing elements.
Accordingly, the object of the present invention is to alleviate or eliminate the disadvantages of prior art.
This object is achieved by a control surface element for an airplane comprising a composite fiber element that has a surface around which air flows, a mounting device for movably mounting the composite fiber element on a structural component, and a reinforcing structure for reinforcing the composite fiber element, wherein said reinforcing structure comprises at least one reinforcing element which is integrally formed with the composite fiber element, wherein said reinforcing structure comprises a primary reinforcing element which is designed to receive main loads and which is connected to at least one secondary reinforcing element that is designed to receive secondary loads, wherein said composite fiber element comprises a recess for integrally forming said primary reinforcing element. Preferred embodiments are indicated in the depending claims.
According to the invention, the reinforcing structure comprises a primary reinforcing element which is designed to receive main loads and which is connected to at least one secondary reinforcing element that is designed to receive secondary loads, the composite fiber element comprises a recess for integrally forming the primary reinforcing element.
Therefore, the invention is based on the fact that the forces introduced into the composite fiber element via the mounting device in operation are not, as in prior art, received by several similar reinforcements, but that according to the invention, the main load is transmitted to a primary reinforcing element which is connected to at least one secondary reinforcing element for receiving secondary loads. According to the invention, the composite fiber element is adapted for a distribution of forces from the mounting device over the primary reinforcing element to the secondary reinforcing element. The primary reinforcing element is embodied as a central reinforcement of the control surface element which reinforcement forms the backbone of the control surface element. To this end, the primary reinforcing element preferably comprises a long stretched-out shape, wherein the secondary reinforcing element is embodied to be weaker than the primary reinforcing element to receive the loads reduced by the primary reinforcing element. To this end, the primary reinforcing element may comprise a larger width and/or height than the secondary reinforcing element. Preferably, several, in particular many, secondary reinforcing elements are provided and are in particular arranged on opposite sides, i.e. towards the front and rear longitudinal side of the composite fiber element. The reinforcing structure with the various reinforcing elements is made of fiber-reinforced plastics.
For an integral embodiment of the primary reinforcing element at the control surface element, the composite fiber element comprises a recess according to the invention. Thereby, a particularly light design may be achieved without compromising the stiffness of the control surface element. For the purposes of the present disclosure, the integral or one-piece embodiment of the reinforcing element means that the reinforcing element is manufactured together with the composite fiber element in a composite fiber structure. In contrast, with a two-piece design, separate composite fiber components are produced which are then connected to each other in a suited manner, for example by adhesive joints.
In the course of extensive theoretical examinations, the design according to the invention surprisingly turned out to be particularly advantageous when it comes to withstanding forces arising in aviation. The control surface element according to the invention in particular permits to transfer non-uniformly distributed loads with a weight-optimized design. Furthermore, load transmission may be effected concentrated on one or several points. It is moreover an advantage that the number of required reinforcing elements may be essentially reduced. Thereby, fabrication efforts may be reduced on the one hand. On the other hand, a particularly weight-saving construction may be achieved which allows for the aircraft manufacturers' constant efforts to reduce fuel consumption. By the integration of at least one of the reinforcing elements, in particular the primary reinforcing element, into the manufacture of the control surface element, fabrication efforts may be advantageously reduced. Moreover, the coherence of the control surface element, in particular in case of major damages, may be reinforced. Thereby, an essential advantage over well-known sandwich constructions with a honeycomb core is achieved. For integrally embodying the at least one reinforcing element, in particular the primary reinforcing element, in the control surface element, in particular the RTM method (Resin Transfer Molding), the method of EP 1 181 149 B1, or the method described in AT 511 113 B may be employed. The embodiment of the control surface element according to the invention is particularly suited for a brake flap (spoiler) which represents one embodiment of a spoiler. The subject matter of the invention is basically suited for further different types of control surfaces, such as aileron, horizontal stabilizer or vertical stabilizer.
To design the primary reinforcing element for higher loads than the secondary reinforcing element, it is advantageous for the primary reinforcing element to comprise a larger width and/or height than the secondary reinforcing element. Accordingly, the loads received in the region of the mounting device are mainly absorbed by the primary reinforcing element which to this end is embodied to be correspondingly stronger than the secondary reinforcing element.
Mainly in case the control surface element is designed as a spoiler, it is advantageous for the mounting device to comprise a mounting element provided essentially centrically at a front longitudinal edge of the composite fiber element which mounting element is adjoined by a central section of the primary reinforcing element. The mounting element is, as is common in prior art, designed to be pivotally mounted at the structural component which, in case of the brake flap, is formed by the airplane's wing box. Such a mounting element in the form of fittings is described in AT 409 482 B. The mounting element is preferably made of a composite fiber material, for example by Resin Transfer Molding (RTM). By arranging the central section of the primary reinforcing element directly adjacent to the mounting element, the loads occurring in this region may be reliably received, secondary loads being introduced into the secondary reinforcing element. To this end, only the primary reinforcing element, but not the secondary reinforcing element, is connected to the central mounting element of the control surface element. Moreover, the mounting device may, as is also common in prior art, comprise further mounting elements at the lateral ends of the front longitudinal edge of the composite fiber element which mounting elements are adjoined by preferably at least one reinforcing element, in particular a secondary reinforcing element.
To laterally remove the main loads acting on the mounting element, it is advantageous for the primary reinforcing element to comprise side sections extending from the central section towards narrow sides of the composite fiber element. For the distribution of the main loads, it is advantageous for the primary reinforcing element to extend at the side sections rearwards, starting from the central section, i.e. away from the front longitudinal edge of the composite fiber element. The primary reinforcing element may be arcuate at the side sections. As an alternative, the primary reinforcing element may comprise linearly extending longitudinal sides.
To distribute forces in the composite fiber element as uniformly as possible, it is advantageous for the side sections of the primary reinforcing element to end adjacent to the narrow sides of the composite fiber element. Accordingly, the main loads are introduced at the central section adjacent to the mounting element and transferred via the primary reinforcing element in the direction of the narrow sides of the control surface element.
Load distribution in the control surface element may be advantageously allowed for if the primary reinforcing element is adapted for receiving higher loads at the central section than at the side sections.
To this end, it is advantageous for the central section of the primary reinforcing element to comprise a larger width and/or height than the side sections of the primary reinforcing element.
Moreover, continuous load transfer may be advantageously effected if the width and/or height of the primary reinforcing element is diminishing outwards at the side sections.
According to a particularly preferred embodiment, the secondary reinforcing element is embodied as a junction of the primary reinforcing element. Accordingly, the secondary reinforcing element branches off like a rib from the primary reinforcing element embodied as a backbone of the reinforcing structure. The secondary reinforcing element may comprise a T-, L-, U- or l-shaped cross-section.
Moreover, the load distribution in the control surface element may be allowed for even more precisely if at least one tertiary reinforcing element is provided as junction of the secondary reinforcing element. The tertiary reinforcing element is weaker than the secondary reinforcing element. To this end, the tertiary reinforcing element may comprise a lower height and/or width than the secondary reinforcing element.
According to a preferred embodiment, the central section of the primary reinforcing element is connected; on a back facing away from the mounting element; with two secondary reinforcing elements arranged essentially in a V-shaped manner and diverging in the direction of the rear longitudinal edge of the composite fiber element. In this embodiment, the flow of forces is therefore received on the back of the primary reinforcing element, split onto the two secondary reinforcing elements diverging in a V-shaped manner and transferred rearwards.
To adapt to the load profile occurring in case of loads it is advantageous for the height and/or width of the secondary reinforcing elements arranged in a V-shape to diminish towards the rear longitudinal edge of the composite fiber element. Thereby, moreover a particularly space-saving design may be created by which the installation situation is considered.
To absorb the remaining loads, it is advantageous if at least one tertiary reinforcing element each projects inwards from the secondary reinforcing elements arranged in a V-shape at the back of the primary reinforcing element. These tertiary reinforcing elements are preferably arranged in a manner converging essentially in a V-shape in the direction of the rear longitudinal edge of the composite fiber element. Thereby, a double-V reinforcing structure is obtained which is particularly suited for compensating loads in the direction of the shorter extension of the control surface element (i.e. in the transverse direction).
According to an alternative preferred embodiment, at least one secondary reinforcing element essentially extending in parallel to the primary reinforcing element is provided and connected to the primary reinforcing element via a connection web in particular extending in the transverse direction of the composite fiber element. In this embodiment, the secondary reinforcing element is shaped corresponding to the primary reinforcing element, however, in view of the lower load absorbing capacity, it has a smaller width and/or height. The connection web permits load transfer between the primary and the secondary reinforcing elements, wherein the connection web preferably extends in the transverse direction of the control surface element, i.e. in case of a brake flap essentially in the direction of flight.
To reinforce the in particular plate-like control surface elements, it is in this embodiment particularly advantageous to provide two arcuate secondary reinforcing elements with a height diminishing towards the rear longitudinal edge which are connected to each other and to the primary reinforcing element via a connection web tapering like a wedge towards the rear longitudinal edge.
To integrally embody the primary reinforcing element at the control surface element, it is advantageous for the composite fiber element to comprise a recess. For the purposes of the present disclosure, the integral or one-piece embodiment of the reinforcing element means that the reinforcing element is manufactured together with the composite fiber element in a composite fiber structure. In contrast, with a two-piece design, separate composite fiber components are produced which are then connected to each other in a suited manner, for example by adhesive joints.
Correspondingly, it is advantageous for the composite fiber element to comprise an indentation for the integral embodiment of the at least one secondary reinforcing element. It is particularly preferred for all primary and secondary reinforcing elements to be integrally formed with the tabular or plate-like composite fiber element, i.e. during the same process or with simultaneous curing. Individual secondary reinforcing elements, however, may also be provided as separate components, in particular composite fiber components, which are connected to the plate-like composite fiber element, for example by an adhesive joint.
In view of an integral construction, it is moreover advantageous for the mounting element to be integrally formed with the composite fiber element for a movable connection with the structural component.
To achieve the control surface element, it is advantageous for the composite fiber element to comprise a lower skin with the reinforcing structure and an upper skin with the surface around which air flows. In this case, the upper skin is designed to be tabular or plate-like. The lower skin is also tabular or plate-like, wherein the reinforcing structure in particular projects therefrom in the form of recesses or indentations. The lower and upper skins are prefabricated as composite fiber components and then connected to each other in a suited manner by adhesive joints or mechanical connections, respectively. In this embodiment, it is advantageous if only the lower skin comprises the reinforcing elements, while the upper skin is free from reinforcing elements. Thereby, a particularly simple design may be created.